Plasticizer blend for cellulose esters

ABSTRACT

A cellulose ester plasticizer blend made from about 40 to 60 percent by weight of glyceryl triacetate with the remainder being primarily a poly(ethylene glycol) diacetate.

United States Patent Touey et al. 1 Feb. 8, 1972 [54] PLASTICIZER BLEND FOR OTHER PUBLICATIONS CELLULOSE ESTERS D.N. Buttrey, Plasticizers, Cleaner-Hume Press Ltd., [72] Inventors. 'loxg, Cephas H. Sloan, both of London 947, Pages 45 and 5L $25255 zikinfi'iF MBriis LieFxfian MW [73] Asslgnee. Kodak Company, Rochester, Assistant Person [2 Fl d J41 l Attorney-William T. French and Daniel B. Reece, III 2] ie: ys, 967 I. I .M [2I] Appl. No.: 650,658 7 I v I I5 1 ABSTRACT 5"- @106/179, 106/ I A cellulose ester plasticizer blend made from about 40 to 60 e percent by weight of glyceryi triacemte with the remainder [58] 7 held ofSearch...", l06/I79, I80, 131/ 267 vLbeing pfimafilyapomethylene glycol) diacetaw [56] References Cited .v 6 ClaimsNo Drawings UNITED STATES PATENTS 2,794,239 6/1957 Crawford et al ..206/59 1 PLAS'I'ICIZER BLEND FOR CELLULOSEESTERS This invention relates to an improved cellulose ester plasticizer type hardening agent which cures the ester very rapidly and has improved hydrolytic stability. More particularly, this invention relates to the use of a blend of glyceryl triacetate (triacetin) and a poly(ethylene gIycOD-diacetate as" percent by weight of glyceryl triacetate to the opened .or

spread out batting. The treated tow is then compacted'or' otherwise formed into the shape of the desired final product.

The glyceryl triacetate plasticizer on the batting functions-as a slow solubilizing agent for the filaments, which may be continuous or staple, thereby slowly dissolving aportion'of the fibers with which it comes in contact. This causes a fusing action' of the fibers at random points of contact throughout the fibrous matrix thus giving the matrix the rigid structureso necessary for subsequent processing. Obviously, the amount of plasticizer added tothe batting must be controlled certain limits since too small an amount wouldnot give sufficient rigidity to the finished fibrous matrix while too'large an amount would fuse too many filaments together thereby producing a structure which is too rigid for many uses.

The action by which the cellulose acetate batting is fused together by the glyceryl triacetate plasticizer is very important since it is accomplished withoutthe application of heat. As'is well known, this gradual hardening of the plasticizer treated batting takes place at room temperature thus eliminating the nature. As mentioned hereinabove, glyceryl triacetate is'an oily substance which gradually hardens the batting at .room temperature after it is fabricated. This is in marked contrast-to the use of so called adhesive types of hardening agents which make the batting tacky assoon as'they are applied. The

use of such adhesive hardening agentsin the manufacture of certain fibrous matrix-type articles is very objectionable'sincethey cause-the staple or continuous batting material toadhere to the fabricating equipment through which it must pass after the application of the hardening agent. Also, the use of adhesives usually implies the need'for removal of either water or an organic solvent which adds both to theequipment necessary and the expense involved inproducing the final product.

Even though glyceryl triacetate is one of the most efficient of the plasticizers which is available for hardening cellulose.

acetate nonwoven materials, and is vastly superior to adhesives, glues, or other solventbasedresins as a hardening agent, it still leaves much to be desired. For example, the freshly prepared glyceryl triacetate containing fibrous matrix must be stored for about 2 hours at room temperature (about C.) before it becomes sufficiently rigid to be cut into smaller segments. This slow curing time often causes the treated fibrous matrix to become deformed or otherwise distorted in shape before it hardens. This is especially true where the fibrous matrix is subject to a loading, as they are stacked on top of-each other before they have had time to cure.

To alleviate some of these limitations of glyceryl triacetate a more recent group of plasticizers has been introduced to the industry. These new plasticizers consist of the acetic acid esters of diethylene glycol, triethylene glycol, tetraethylene lanweight to about 700-1000. These new acetic acid esters are superior to those prior known plasticizer bonding agents in that they harden the plasticizable fibrous matrix at room temperature in ashorter length of time (about minutes as opposed to 2 hours for-glyceryl triacetate).

However, althoughthe acetic acid ester plasticizers have a fasterbonding action than glyceryl triacetate, they have certain limiting characteristics-which are not common to glyceryl triacetate. One problem is that they are more hygroscopic than .glyceryl-tri'acetate. That is, they absorb moisture more readily and therefore become contaminated with water if they are exposed'tomoistair. This makes storage of the'material in air vented'tanks on humiddays somewhat of a problem. Also the presence of water in the water-miscible ester makes it more susceptibleto hydrolysis, and hydrolysis leads to the formationof trace'amou nts'of'acetic acid which is quite objectionable-ifthe fibrous matrix is to come into close contact with an individual.

Thus, it can be seen thatthe development of a new and improved'bonding orhardening agent for cellulose acetate tow would represent a substantial step forward in the fibrous matrix orbatting field. As will be appreciated, any new bonding or'hardening agent must-have no unpleasant odors as is characteristic of plasticizers that hydrolyze. The plasticizers foruse onnonwoven-staple of fibrous materials must also be nontacky and, ideally, less expensive to produce and use than bondingagents now available. Furthermore, these new bonding agents-should be capable of hardening thefibrous matrix at-roorn temperature in a shorter period of time than was heretoforerequired.

Accordingtto the-present invention it has been found that a new and superior group or blend of bonding or hardening agents for continuous or staple cellulose ester fibers can be produced which are nontacky and will harden the cellulose fibers in ashorter period of time than heretofore thought possible. Furthermore, these new blends of bonding or hardening: agents are less expensive to produce and will hardenacellulose; ester fiber at room temperature.

According-to one-embodiment of this invention, the rapid bonding plasticizer formulation comprises from about 40 to percent'by weightt ofglyceryl tria'cetate blended with from about 60 to 40' percent by weight of a poly(ethylene glycol) diacetate. Normally the poly(ethylene glycol) diacetate is selected from the 'group'consisting of di-, tri-, tetra-, penta-, and heptaethyleneglycol-diacetate. It was quite unexpectedly discovered that by .carefully controlling the percent of polyethylene glycol) diacetate blended with glyceryl triacetate a bonding or hardening agent could be produced which would harden a cellulose ester type batting at room temperature in a shorter period of time than could'be obtained by using either the glyceryl triacetate or poly(ethylene glycol) diacetate alone.

Therefore an object of this invention is to disclose a new plasticizer blend which is capable of hardening a cellulose ester batting inan extremely short period of time.

Another objectof thisinvention is to disclose a more rapid bondingplasticizer for batting prepared from staple or continuouscellulose ester filaments.

A -further object of this'inventionis to disclose a more rapid plasticizer bondingagentthat-has a less tendency to hydrolyze when exposed to'a'humid atmosphere than that exhibited by the acetic=acidestersof the -ipoly(ethylene glycol) diacetates heretoforeusedbyth'e fibrous matrix industry.

an'd otherobjects and advantages of this invention will be more apparent upon reference to the accompanying specification, specific working examples, and appended claims.

As briefly set out hereinabove, this invention involves the blending together of selected amounts of glyceryl triacetate (triacetin) and po ly( ethylene glycol) diacetate to'produce a bondingagent'forcellulose acetate which is less expensive, will '-react-faster to harden*the-materials,and-is readily adaptaglycol andsuchpoly(ethylene glycols) which have a molecuble for use in thefibrous matrix field. The percentage of glyceryl triacetate blended with the poly(ethylene glycol) diacetate wherein is quite critical and has been found to extend within the range of from 40 to 60 percent by weight glyceryl triacetate and from 60 to .40 percent of a poly(ethylene glycol) diacetate, which can be represented by s qw psfsrus wherein O and n=2 to 6. That is, the poly(ethylene glycol) diacetate is :chosen from the group consisting of diethylene glycol 'diacetate, triethylene glycol diacetate, tetraethylene glycol diacetate, pentaethylene glycol diacetate and hexae'thylene glycol diacetate. The preferred poly( ethylene glycol) diacetates for blending with glyceryl triacetate are the di-, tri-, and tetra-, ethylene glycol diacetates.

As will be appreciated by those working in the fibrous cellulose ester matrix field, it was entirely unexpected to find that when a slower bonding plasticizer (glyceryl triacetate) is blended with a faster bonding plasticizer (the glycol diacetates) one would obtain a combination or blend which bonds an acetate matrix even more rapidly than does the faster plasticizer when used alone. One would expect that a retardation of the more rapid bonding action of the faster bonding plasticizer would occur when it is diluted by the addition of the slower bonding plasticizers. it is equally surprising to discover that if more or less than 40 to 60 percent by weight of poly(ethylene glycol) diacetate is blended with the glyceryl triacetate, the hardening time of the blend will be adversely affected. That is, the time required for a fibrous cellulose acetate matrix to harden to an acceptable level will be greatly increased. As will be appreciated, this complete plasticizer; reaction time and critical blend range is an unusual:

phenomenon which could not be predicted by what was previously known in the field.

The reason or theory for this synergistic effect of the combination of the two plasticizers or the critical ranges involved is not clearly understood. However, one explanation could be the face that cellulose ester fibers, such as cellulose acetate, are not highly homogeneous polymers since they'have both long and relatively short chain units in their structure as well as having varying degrees of acetyl content within any given segment of a fiber. Therefore, the blend of the two bonding plasticizers might be complementing one another to form a more satisfactory solvent for the polymers than either one of the plasticizers alone, for it is the solvent effect of the plasticizer on the cellulose ester fiber which fuses the fibers into a rigid structure.

' point where the fibers are compacted or otherwise formed into an end product. Another way of adding this high boiling liquid hardening agent to the two is to employ a wicking device which wipes" the desired amount of liquid on the bloomed-out batting at some point during its travel through the processing equipment. However, regardless of the method or. apparatus used in evenly dispersing the plasticizer hardening agent, it has been found that the amount of agent used can vary within a wide range, but if a porous matrix is to be fonned then from 4 to 20 percent based on the total weight of the matrix is normally used. Less than about 4 percent of the blend usually results in a matrix which is not as firm as is normally desired in the trade. Increasing the amount of above 20 percent does not usually give an additional advantage unless a solid, nonporous matrix is desired.

A further understanding of the invention will be had from a consideration of the following examples which may be used in actual commercial practice of the invention and which are set forth to illustrate certain preferred embodiments and features EXAMPLES A cellulose acetate web or tow consisting of 15,000 crimped cellulose acetate fibers is spread out or bloomed to form a band of approximately 14 inches in width. The bloomed band of cellulose acetate tow is then treated with the various plasticizers or blend of plasticizers shown under the heading Plasticizer Formulation" in Table 1. This treating of the bow with the plasticizer fonnulations is accomplished by changing the type of plasticizer in the spray booth at different intervals during the continuous preparation of cellulose acetate two by a technique similar to that described in U.S. Pat. No. 2,794,239. in each case the amount of plasticizer added to the opened tow during its progress through the fibrous matrix forming machine is held within the range of 7.5 and 8.5 percent by weight based on the total weight of the fibrous matrix. Immediately after the plasticizer treatments the rapidly moving tow can be recompacted into a tight bundle and drawn through a device that wraps it in a paper if this is necessary or desirable. Additional processing steps can also be performed on the treated tow or matrix at this point.

After having been treated with the proper amount of plasticizer and formed into the desired shape, the treated tow or matrix is permitted to cure at 75 t2 F. At predetermined time intervals the treated tow or matrix is tested by subjecting it to a sudden load of 347.5 grams for 10 seconds. A deformation of more than 1.4 mm. is considered sofl; 1.1 to 1.4 mm., semifirm; 0.7 to 1.0 mm, firm; and below 0.7 mm. rigid.

TABLE I Hardness rating of the batting Example Plasticizcr formulation 5 min. 10 min. 20 min. 30 min.

1.- Glyceryl triacetate Solt Soft Soft Semi-firm. 2.- Diethylene glycol diacetatc. .do Semi-firm"... Firm Rgtd. 3-- Triethylene glycol diacetate do 4.. Tetraethylene glycol diacetate 5--.. Pentacthylene glycol diacetato 6.-.. 70% dicthylene glycol dlacctate-30% glyceryl triacetate- 7--.. 60% dicthylcne glycol diacetate-% glyceryl triacetate. 8.... diethylcne glycol diacetate-50% glyceryl triacetate. 0.- 40% diethylene glycol diacetatc-% glyceryl triacctate. 10- 30% diethylene glycol diacetate-% glyceryl trlacetatc- 11. 70% tricthylene glycol diacetate-30% glyceryl triacetatc 12- 60% triethylene glycol diacetate-40% glyceryl trlacetate... 13. 50% triethylene glycol diacetate-50% glyccryl trlacctate-..- 14--. 40% trlethylene glycol dlacetate-60% glyceryl trlacetatc 15 30% trlethylenc glycol diacetate-70% glyceryl UlBCBtSIO...

16... 70% tetracthylenc glycol diacetato-30% glyceryl trlacctate. 17... 60% tstracthylcno glycol diacetate-40% glyceryl trlacctate- 18.. 50% totrnothylcnu glycol diucotste-50% glyceryl trlacctatc. 10.. 40% tctrncthylonc glycol dlacotato-60% glyccryl trlacstntc. "0 30% tutmotliylono glycol diamante-70% glyccryl triacctato.

709;, pcntnothylcnoglycol d1ncotste-30% glycoryl trlncetatc. (i001, pontucthylono glycol (acetate-40% glyccryl trlucctnto.

50% pontncthylonc glycol dlncctato-50% glycoryl trlucetnte-.. 40% pcntscthyleuc glycol discotate60% glyccryl trlscctato... 25 30% pentacthylcne glycol diacctatc-70% glycoryl triacctate As will be apparent, these above examples clearly illustrate how certain blends of glyceryl triacetate and a poly(ethylene. glycol) diacetate bond a cellulose acetate batting into a rigid structure more rapidly than does either the glyceryl tl'iacetate or. poly(ethylene glycol) diacetate alone.

As mentioned briefly hereinabove, several different poly(ethylene glycol) diacetates can be mixed together and the correct percentage of the mixture (i.e., 40 to 60 percent by weight) can then be blended with from 40 to 60 percent by weight of glyceryl triacetate to give the desired plasticizer. For example, the following mixtures of poly(ethylene glycol) diacetates can be prepared:

To produce a batting or nonwoven product using a plurality of poly(ethylene glycol) diacetate blended with from 40 to 60 percent by weight of glyceryi a tow or batting material consisting of 15,000 crirnped cellulose acetate fibers is spread outor bloomed to form a band of approximately 14 inches in width. The bloomed band of celluloseaeetate batting is then treated with the various blend of plasticizers shown under the heading "Plasticizer Formulation" in Table ll. This treating of the batting with plasticizer formulations is accomplished by changing the type of plasticizer in the spray booth at difi'erentintervals during .the continuous preparation of cel- TABLE I Hardness rating of the batting Plastioimr Cnrmulmfiuu 5 min. 2Q t V. 7021 iurmulution A 603, glytlm'fl misnomer-s-.. Sol'l. Selm'iirrn liig-ni.

00% formulation A407 glyceryl triacetate .tlc Rial 60% formulation A50% glyceryl triaeetate--. 40% formulation A-60% glyceryl tr1acetate- Firm 30% formulation A-70% glyceryl triacetate D0 31 70% formulation -30% glyceryl triacetate. 32... 60% formulation 13-40% glyceryl triaeetate. 33--. 50% formulation 13-50% glyceryl triacetate 34 40% formulation 13-60% glyceryl triacetate.

formulation B-70% glyceryl triacetate. 70% formulation 030% glyceryl triacetate. 60% formulation 040% glyceryl trlacetate..- 50% formulation C-50% glyceryl triacetate... 39. 40% formulation C-60% glyceryl triacetate d 40 30% formulation C-70% glyceryl triacetate do Semi-firm Formulation 30 W rpm W Designation Plasticizer Formulation acefate filter described U.S. Pat-No. 2,794,239. In case the amount 10 parts per l00 I methylene glycol diam: of plastlclzer added to the opened tow its progress N 5 Pam per loo through the filter plug making machine is 7 held the A "iflhyleneglyw'dacm 5 allsw Z5 a d sw a y ws s ltlaasid 9 th; .299 g' i 'zgig weight of the batting product. Immediately after these ia plasticizer treatments the rapidly moving batting is recoms: $253 3? pacted into'a bundle which can then be drawn through a diacetate i e fla ware ti s tali sm terialleaprtl f such is 35:3 :32? necessary or desirable. The formed batting is now stored at 75 diaceme :2 F. to cure and are tested at predetermined time intervals 5 P P" Q to determine rod hardness. dlethylene glycol dlacetate W7 10 parts per 100 From the several examples g ven in Table II it can be seen triethylene glycol diacetate that mixtures of several poly(ethylene glycol) diacetates can B f P be blended with from 40 to 60 percent by weight of glyceryl diaceme y 8 triacetate to give a plasticizer blend having unique properties. 60 parts per 100 As will be appreciated, this is an important consideration since it is often necessary or desirable to use such poly(ethylene m pans 100 glycol) diacetates mixtures rather than attempting to obtain a hexaethylene glycol pure material having only one poly(ethylene glycol) diacetate dlacetate 5 parts per 00 h i diethylene glycol diacemc To determine the hydrolysis of various plasticizers or 5 parts P 0 iplastlcizer blends shown under the heading Plasticizer For- C ggi'f ga gg =mulations in Table III, these bends are placed in open petri tetmmylena glycol dishes and the dishes stored for days in a chamber maindiacctate tained ata temperature of 80 F. and a relative humidity of zgg 'gxi g? percent. The amount of water and acetic acid that will be diam 5 foundin the various samples at the end of the 60 day period is 30 Pm per mo 0 W a. i From the examples of Table 111 it is apparent that the addiqn qtslyqsrxlifia tats taapp xlstl i snss zsq diaceme TABLE III Percent water Percent acetic acid Ex. Plastlcizer formulation At start 60 days At start 60 days 41 Glyceryl triacctate r. 0.02 0. 5 0.002 0.10 Diethylens glycol diacetato 0.02 3.0 0.02 1.00 43 50 parts glyceryl trlacetate and 0.02 1. 0 0.01 0. 40

60 parts diethylene glycol diacetate. Triethylene glycol diacetate 0. 02 2. 2 0. 01 0. 50 parts gly'ceryl triacetate and 0.02 0.8 0.005 0.30

50 parts triethylene glycol diacetate. 46 Tetraethylene glycol diacetate 0.02 1. 0 0. 01 0. 50 47 50 parts glyceryl tn'acetate and 0.02 0.6 0.005 0. 15

50 parts tetraethylene glycol diacetate.

greatly reduces its capacity for absorbing water and liberating acetic acid when stored under humid atmospheric conditions.

As will be appreciated, this reduction in the hydrolysis of the blend is of utmost importance in the production of batting or nonwoven products which will come into contact with the human body.

From the foregoing it will be obvious that the use of these new cellulose ester hardening agents offer numerous advantages over any other such agents heretofore used in the industry. For example, they cure or harden an acetate batting material at room temperature more rapidly than any other plasticizer of the nontacky, high-boiling liquid type. The fact that they are odorless, tasteles, and adapted for use in existing commercial equipment is of prime importance.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

We claim:

1. A bonding plasticizer blend comprising from about 40 to 60 percent by weight glyceryl triacetate and from about 60 to 40 percent by weight of at least one poly(ethylene glycol) d te av nsas yqwalfqrmy a wherein and F2 to 6.

2. Bonding plasticizer blend according to claim 1 wherein the poly(ethylene glycol) diacetate is selected from the group consisting of diethylene glycol diacetate, triethylene glycol diacetate, and tetraethylene glycol diacetate,.

3. Bonding plasticizer blend according to claim 1 wherein about 40 to -50 percent by weight of glyoeryl triacetate is blended with about 60 to 50 percent by weight of poly( ethylene glycol) diacetate.

4. Bonding plasticizer blend according to claim 3 wherein the poly(ethylene glycol) diacetate is selected from the group consisting of diethylene glycol diacetate, triethylene glycol diacetate and tetraethylene glycol diaeetate.

5. Bonding plasticizer blend according to claim 1 wherein about 50 percent by weight of glyceryl triacetate is blended with about 50 percent by weight of poly(ethylene glycol) diacetate.

6. Bonding plasticizer blend according to claim 5 wherein the poly(ethylene glycol) diacetate is selected from the group consisting of diethylene glycol diacetate, triethylene glycol diac tat a d id n 5139!???49 

2. Bonding plasticizer blend according to claim 1 wherein the poly(ethylene glycol) diacetate is selected from the group consisting of diethylene glycol diacetate, triethylene glycol diacetate, and tetraethylene glycol diacetate.
 3. Bonding plasticizer blend according to claim 1 wherein about 40 to 50 percent by weight of glyceryl triacetate is blended with about 60 to 50 percent by weight of poly(ethylene glycol) diacetate.
 4. Bonding plasticizer blend according to claim 3 wherein the poly(ethylene glycol) diacetate is selected from the group consisting of diethylene glycol diacetate, triethylene glycol diacetate and tetraethylene glycol diacetate.
 5. Bonding plasticizer blend according to claim 1 wherein about 50 percent by weight of glyceryl triacetate is blended with about 50 percent by weight of poly(ethylene glycol) diacetate.
 6. Bonding plasticizer blend according to claim 5 wherein the poly(ethylene glycol) diacetate is selected from the group consisting of diethylene glycol diacetate, triethylene glycol diacetate, and tetraethylene glycol diacetate. 